[July 5th 2005]
The 'docs' directory contain various text files that should help you
understand the most importants classes in MediaWiki.
API documentation is sometime generated and uploaded at:
http://svn.wikimedia.org/doc/
You can get a fresh version using 'make doc' or mwdocgen.php
in the ../maintenance/ directory.
For end user / administrators, most of the documentation
is located online at:
http://meta.wikimedia.org/wiki/Help:Help